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A156031 Alternate A022941 and A143344. 4
1, 2, 3, 5, 4, 9, 6, 15, 7, 22, 8, 30, 10, 40, 11, 51, 12, 63, 13, 76, 14, 90, 16, 106, 17, 123, 18, 141, 19, 160, 20, 180, 21, 201, 23, 224, 24, 248, 25, 273, 26, 299, 27, 326, 28, 354, 29, 383, 31, 414, 32, 446, 33, 479, 34, 513, 35, 548, 36, 584, 37, 621, 38, 659, 39, 698 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Eric Angelini's definition was: start with 1,2,3; then alternately adjoin either the sum of the last two terms or the smallest number not yet in the sequence.

LINKS

M. F. Hasler, Table of n, a(n) for n = 1..2001

PROG

(PARI) f="b156031.txt"; used=[]; write(f, c=1, " ", b=1); a=1; for(i=1, 1e3, used=setunion(used, Set(a+=b)); while(setsearch(used, b++), used=setminus(used, Set(b))); write(f, c++, " "a"\n", c++, " "b)) \\ M. F. Hasler, Nov 01 2009

(Haskell)

import Data.List (transpose)

a156031 n = a156031_list !! n

a156031_list = tail $ concat (transpose [a022941_list, a143344_list])

-- Reinhard Zumkeller, May 17 2013

CROSSREFS

Cf. A022941, A143344, A167151, A005228, A030124.

Sequence in context: A074050 A269368 A075301 * A119475 A096116 A259431

Adjacent sequences:  A156028 A156029 A156030 * A156032 A156033 A156034

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Nov 01 2009, based on a posting by Eric Angelini to the Sequence Fans Mailing List

STATUS

approved

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Last modified December 2 23:36 EST 2020. Contains 338898 sequences. (Running on oeis4.)